Regarding the First Invention
A layered product comprising resin layers and metal thin film layers is used in a wide range of applications, for example, as a magnetic recording medium such as a magnetic tape, a wrapping material or an electronic component.
The resin layers used in such a layered product are produced by melting and stretching a resin material into a self-supported film or by applying a solution of a resin material diluted with a solvent to a supporting base and drying the resin for curing. However, the smallest thickness of the resin layer obtained by these methods is only about 1 μm, and neither of the above methods can produce thinner resin layers stably. Moreover, the former method tends to require large scale equipment. In the latter method, some solvents are not preferable to be used for environmental reasons, and defects tend to be generated in the coating film after drying.
As a method for producing thin resin layers stably that does not cause any of the above problems, a method of forming a resin thin film on a supporting base in a vacuum has been proposed. In this method, a resin material is evaporated in a vacuum and applied to a supporting base to produce thin films. It is said that this method allows resin thin film layers without void defects to be formed.
On the other hand, for formation of metal thin film layers, a method of vacuum evaporation on a surface of a supporting base that is moving at high speed is advantageous for mass production and is put in industrially practical use.
Primarily in the application as electronic components and other applications as well, patterning of metal thin film layers, namely forming metal thin film layers only on a specific region, is performed. For example, a metal thin film layer can be divided into a plurality of sections by forming an insulating region where no metal thin film layer is formed, so that metal thin film layers having different electric potentials can be formed in a layered product.
Oil margin is a known method for patterning the metal thin film layer. This method utilizes the following principle. When a patterning material such as oil is previously formed in a small thickness on a supporting base, and then a metal thin film is formed by metal evaporation or the like, a metal thin film layer is not formed on the patterning material.
The recent needs for a layered product including resin layers and metal thin film layers are directed to further degrees of compactness, high performance and low cost. For example, various required characteristics are satisfied or a specific function is provided by depositing a plurality of deposition units comprising resin layers and patterned metal thin film layers. In this manner, efforts have been made to achieve both compactness and high performance. Moreover, efforts have been made also to achieve a low cost by depositing layers for a layered product comprising resin layers and metal thin film layers continuously on a rotating supporting base.
However, in production of a layered product by depositing a number of layers alternating a resin layer and a metal thin film layer on a rotating supporting base, when depositing a metal thin film layer in a specific region by applying a patterning material in a specific shape after deposition of the resin layer and before deposition of the metal thin film layer, problems such as chapping of the surface of the deposited layers, pinholes (lack of deposition) of the resin layer or the metal thin film layer, instability of the deposition region of the metal thin film layer (e.g., deposition is beyond the limit of the desired deposition region or is short of the desired deposition region) or the like turned out to be caused. These problems were not caused in a conventional method for producing a two-layered product simply by applying a patterning material to a resin layer and then forming a metal thin film layer. In addition, these problems tend to be more significant with decreasing deposition thickness of each layer.
Regarding the Second Invention
The current need for compactness and high performance of electronic components is increasingly strengthened, and this is the case also for capacitors. The capacitance of the capacitor is in proportion to the area of the dielectric and in inverse proportion to the square of the thickness of the dielectric layer when the dielectric constant of the dielectric is the same. Therefore, in order to achieve a compact capacitor and maintain or increase the capacitance thereof, it is effective to make the dielectric layer thin and increase an effective area of a region where capacitance is generated.
One known example of a layered product comprising dielectric layers and metal thin film layers used for electronic components such as capacitors is a layered product for a film capacitor. This layered product is formed by layering or winding a metallized film obtained by depositing a metal thin film such as aluminum on a resin film such as polyester (e.g., PEN, PET), polyolefin (e.g., PP) or PPS by vacuum evaporation, sputtering or the like.
However, there is a limit for the thickness of the resin film due to various constraints such as handling properties or processability of the film during or after production. The smallest thickness of currently used film capacitors is about 1.2 μm. Thus, making a thinner dielectric layer and increasing the effective area of the capacitance generation portion while maintaining the volume of the capacitor have reached the limit, thereby preventing the achievement of both compactness and high capacitance of the film capacitor.
On the other hand, a layered product for a capacitor comprising a dielectric layer and a metal thin film layer produced by a method totally different from that for the conventional film capacitor, which allows the thickness of a dielectric layer to be about lam, has been proposed (Japanese Patent (Tokko-Sho) No. 63-31929, U.S. Pat. No. 5,125,138 or the like).
However, the capacitor disclosed in Japanese Patent (Tokko-Sho) No. 63-31929 has a structure where a metal thin film layer (electrode layer) is inclined to the deposition direction so as to be in contact with the side of the capacitor, thereby forming electrodes. Therefore, the metal thin film layer is likely to be ruptured in the inclined portion of the metal thin film layer. In addition, the appearance thereof is significantly different from that of a conventional chip film capacitor, so that special consideration for mounting is required.
On the other hand, U.S. Pat. No. 5,125,138 discloses a layered product where the metal thin film layer (electrode layer) is exposed at the side of the layered product without being inclined. However, the deposition thickness is significantly different between a portion where a small number of metal thin film layers are deposited and the other portions in the overall layered product. Therefore, a recess is generated on the upper surface in the deposition direction in the portion where a small number of metal thin film layers are deposited. This recess deteriorates the handling properties when mounting the layered product onto a printed circuit board with a solder and adversely affects the wettability of the solder. Moreover, since the dielectric layer and the metal thin film layer are inclined or curved in the vicinity of the recess, the deposition thickness is small, thus leading to a drop of the withstand voltage, pinholes of the dielectric layer, poor conductivity of the metal thin film layer or the like, when the layered product is used as a capacitor. Furthermore, such a recess makes it difficult to produce the layered product itself. The recess is generated more significantly with decreasing thickness of the dielectric layer (e.g., 1 μm or less) and with increasing the number of depositions (e.g., 100 or more, particularly 1000 or more). Therefore, in such a layered product, it was still difficult to achieve both compactness and high capacitance of the capacitor.